Tuesday, December 14, 2010

Ecological Disaster - a Quarter of a Billion Years Ago

"Massive Volcanism May Have Caused Biggest Extinction Ever"
Alexandra Witze, Science News, via Wired Science, Wired (December 14, 2010)

"The greatest extinction in the history of life may have been caused, in part, by ozone-depleting gases spewed in a massive volcanic eruption, a new study suggests. Geologists have found surprisingly high amounts of the elements fluorine and chlorine in Siberian lavas dating back 250 million years — when about 90 percent of marine species and 70 percent of terrestrial species went extinct.

"Benjamin Black, a graduate student at MIT, and his colleagues described their theory Dec. 13 in a poster presentation at a meeting of the American Geophysical Union.

"Researchers have long struggled to explain the 'Great Dying' that occurred at the end of the Permian period. Some think that the extinction was a long, drawn-out affair caused by multiple factors - perhaps gradual changes in oceanic or atmospheric chemistry (SN: 5/28/05, p. 339). Others have blamed a single catastrophic event such as a belch of methane from the seafloor or an asteroid impact (SN: 2/24/01, p. 116) like the one thought to have wiped out the dinosaurs and other species 65 million years ago.

"Volcanoes might be one of those calamities. In Siberia, around 250 million years ago, a series of massive volcanic eruptions spewed out lava over more than 2 million square kilometers [800,000 square miles]. Some scientists have blamed these eruptions, known as the Siberian Traps, for climatic changes that contributed to the extinction...."

Between routine events like eruptions that created the Siberian and Deccan Traps, the Yellowstone caldera's periodic blowup, and intermittent falling asteroids, this planet isn't a particularly safe place to live.

The Siberian Traps are interesting, according to this article, because there's significantly more sulfur, chlorine and fluorine in those rocks than in the Deccan Traps.

"...The chemicals probably weren't in the magma as it began traveling up from deep within the Earth, the team proposed, but melted into the magma as it passed through salt-rich rock before erupting on the surface.

"In all, the amount of chemicals in the Siberian rocks could translate to 9 trillion tons of sulfur, 8.5 trillion tons of fluorine and 5 trillion tons of chlorine spewing into the atmosphere during the eruptions. Such elements, when pumped out by power plants, can cause acid rain locally...."

That's trillions of tons: a whole lot of very reactive chemicals. Whatever else was going on at the time, that stuff in the atmosphere wasn't making conditions any better.

Although, if this hadn't happened, the Lemming wouldn't be writing this post - and you wouldn't be reading it.

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